In the electronics field for contemporary semiconductor devices, the charge degree of freedom that electrons have is used, and electrons have the spin degree of freedom in addition to that of charge.
In recent years, spintronics where this degree of freedom regarding spin, that is to say, the degree of freedom regarding spin angular momentum, is used has attracted attention as a carrier for information technology for the next generation.
In this type of spintronics, the aim is for the degree of freedom that electrons have regarding charge and spin to be simultaneously used so that new functions and characteristics can be gained. Most of the spintronic functions are driven by a spin current.
Spin currents have little energy that is scattered and lost, and therefore, the probability of a spin current being used for efficient information conveyance is high, and thus, a method for generating and detecting a spin current is urgently required to be established.
As for a method for generating such a spin current, a spin current resulting from spin pumping that can be compared to a current resulting from electromagnetic induction has been proposed (see Non-Patent Document 1, for example), and a spin current resulting from excitation by circularly polarized light that can be compared to a current resulting from photovoltaic power has also been proposed.
In addition, as for a method for detecting a spin current, the present inventors have proposed a method for detecting a spin current using an inverse spin Hall effect, and have found that a current flows in the direction perpendicular to the direction of the pure spin current when a pure spin current is injected into a sample, and thus, there is a difference in potential between the ends of the sample when this inverse spin Hall effect is used, and therefore, it is possible to detect the existence of a flow of a pure spin current by detecting this difference in potential (see Non-Patent Document 2, for example).    Non-Patent Document 1: Phys. Rev., B19, p. 4382, 1979    Non-Patent Document 2: Applied Physics Letters, Vol. 88, p. 182509, 2006